Early convection/initiation is by far the biggest failure mode with both Friday and Saturday. With Thursday, it's that the wave slows too much or the moisture return is less than advertised.Model consensus growing for a multi-day, upper end severe weather episode from Friday 4/27 through next Tuesday.
Looking for a failure mode and can't find one. Ample CAPE everywhere, plenty of shear, favorable LCL heights and limited capping.
That said, there could be two factors that either reduce the ceiling on this system:
1. The highest shear does seem to be displaced from the best CAPE during some the 27th-1st period. But for most of that time frame, some shear is present in most of the warm sector. Otherwise, shear and CAPE are overlapping quite well.
2. Ongoing convection could reduce atmospheric recovery. However, model's don't seem to be concerned with moisture quality. This is a slow moving storm and very moist area will be advecting into the warm sector very efficiently for several days.
Interestingly, NE IL/SE WI (Chicago, Milwaukee, Madison) area might be a good chase target for late evening on April 27th and perhaps again on April 28th.